Bolt
joint under dynamic loading 

Metric thread : 
 
Initial tensile stress : σ_{i} 
·R_{p0.2} 
Minimum value of clamping force: F_{m} 
kN 
Joint stiffness factor C_{m}=k_{b}/(k_{b}+k_{m}) 


tensile stress area A_{t }
=π/4 d_{0}^{2 }; d_{0}=(d_{2}+d_{3})/2 
mm^{2} 
ultimate tensile strength R_{m} 
MPa 
yield strength R_{p0.2} 
MPa 
initial tensile stress σ_{t} =
α R_{p0.2} 
MPa 
load at yield F_{0.2 }= R_{p0.2} A_{t} 
kN 
initial preload F_{i} = σ_{t} A_{t} 
kN 
load fluctuation bolt P_{b }=F_{0.2 } F_{i} 
kN 
amplitude of bolt stress σ_{at }=
½P_{b }/A_{t} 
MPa 
endurance strength of the bolt σ_{e} 
MPa 
load fluctuation clamped material P_{m}= P_{b }
(1C_{m})/C_{m} 
kN 
clamping force F_{m }= F_{i }P_{m} 
kN 
Total load fluctuation P_{ }=
P_{b} + P_{m} 
kN 
Warning: Amplitude of dynamic bold stress > Endurance Strength:
In infinite life or safe stress designs stresses higher then the
endurance limit are avoided and a factor of safety is taken into
account. Most rotating and oscillating components must sustain
over 10^6 load cycles during service life and thus are to be
designed for infinite fatigue life. 

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